There is no real limit to how many flowgraphs you can have on the one
entity, but there are some guidelines you should follow. Firstly for
each xml you plan on opening/saving using the Flowgraph Plugin System
you should have a separate flowgraph. Secondly, you may have issues
with syncronisation if lots of flowgraphs are based on a single entity
and rely on timers or delays - for example, if all the flowgraphs are
set to start when a timer gets to 5 seconds, there may be a bit of lag
for some.
As for making things glow, Vinh has a tutorial in the Week 2 notes
that covers how to change the glow of the player character. The same
node Entity:MaterialParam can be used for any entity to change the
glow. The sub material ID (SubMtlID) will most likely need to be
changed for the entity you are using, and will most likely be 0 if the
entity is your own creation from sketchup. Otherwise use the
eyedropper in the material editor to identify the sub material ID of
the material to wish to change.